Machine tools having a spindle housing in which a shaft is journaled for rotation and to which a tool can be affixed are in common use. For example, the tool may be a borer or drill received in a tapered socket and driven, by its coupling with the shaft, at high connecting speeds. Other tools of this type may be end mills, milling cutters in general, shaping tools and the like.
It is important, depending upon the application of the machine, to be able to deliver coolant with high pressure and preferably at various locations to the machining site and to various parts of the tool while nevertheless allowing the tool to be rotated at high rotary speeds. The coolant can also serve to carry away the machining detritus, such as chips, turnings and the like.
For this purpose it is known to provide at the rear end of the spindle housing, a coolant supply system or line which is provided with a rotary connection to the shaft or to the rotating member of the system, e.g. a tool. The shaft may have a flange which rotates with the tool and to which the tool is connected. Within this liquid supply system, a passage is commonly provided for delivering the coolant to the tool, e.g. a drill bit or boring tool and communicating centrally therewith.
It has already been proposed to provide in a conical shaft system having a socket or a tool, an off-center opening for the coolant or lubricating liquid so that corresponding types of tools can be fed with the liquid. In other words, somewhat newer tools generally have an off-center coolant/lubricant passage requiring an off-center supply passage in the socket or rotating part of the assembly while older tools continue to have the central passage which must be supplied through a central passage in the rotating part.
For machine tool manufacturers, this poses a problem since the machine tool must be equipped for one or the other of these two types of tools which may be used and either with the new off-center supply or with the old central supply.
In the past, it has been difficult, if not impossible, to reconstruct a machine tool built for one type of tool to accommodate the other type.